The Arithmetic of Compassion
by V.M. Bell
Summary: Regulus," she says slowly, "I hope that, when you are your brother’s age, you are not nearly so difficult."


**The Arithmetic of Compassion**

It is with a hushed anticipation that Regulus leans over his desk and peers through his window. Four people stand on the sidewalk; there is conversation, laughter, and as Regulus squints, he thinks he sees the two youngest among them trade smiles. They lean in for a hug, clasping one another for a moment. Then three of the four people turn, walk away, and one dark-haired boy is left standing with only a worn trunk and caged owl for company.

The front door creaks open, and Regulus instantly busies himself with his original preoccupation. He has tried writing this letter to Cousin Bellatrix twice now; both of these attempts lay crumpled at the foot of his bed, and he knows that he will have to redo his third attempt. It would not do, he reasons, to send a letter filled with strikethroughs and messy handwriting to Cousin Bellatrix. Nothing, he reminds himself, nothing must be left in doubt, and she will --

Suddenly, Regulus senses someone shuffling across the hallway outside his room. Frowning, he gets to his feet and looks outside his bedroom door.

"Mistress?" The family's ever faithful house-elf scratches at her door, and Sirius is halfway up the stairs, hand frozen on the banister as he glares at Kreacher. "Mistress, the young master is home."

He looks at Sirius, but Sirius does not look back. Then Mother's door opens and Regulus looks away, his heart struggling against its restraints.

"So," she says. Her voice is low, perfectly calm. "You're home."

"I am indeed, Mother."

The staircase squeaks.

"The summer holidays began -- oh, they began three days ago, did they not?"

A pause. "They did, Mother."

"Your brother Regulus arrived home three days ago, just as he was expected to." Regulus shuts his eyes tightly. "Can you imagine my surprise when he arrived home with no older brother to accompany him?"

"Regulus is bloody well old enough to go home without me."

There is some stomping and muttering before Mother's voice cuts through the din. "Sirius," she says, infinitely calm.

Regulus forces himself to look at her. She is older now than she once was, but the lines on her face only serve to accentuate their natural angles. She has always been a sharp woman in both appearance and manner. The years have deepened this, and all her hushed fury is now directed towards her wayward son. Regulus knows that his brother dislikes her -- loathes her, even, if it is even possible for a son to loathe his mother -- but there is somewhat in her voice that he still cannot disobey. He does not seek to slip from her gaze but does as she says and stands, motionless, beneath her unforgiving verdict.

"Three days." Mother leaves the confines of her room, each step a challenge to Sirius's rebellion. She folds her arms against her chest, Kreacher at her side. "For three days, you have been missing from his house. Where have you been?"

Sirius mumbles.

"Louder."

"With James," he says, a glint steeling his black eyes.

Mother quirks an eyebrow. "With the Potters?"

Regulus thinks he sees Sirius roll his eyes, but rolling one's eyes in Mother's presence --well, that is a dangerous thing to do. "Yes, the Potters."

"So." Mother smirks, her lip curling in that peculiar way. "You spend three days in the company of blood traitors. What more, you neglect to tell me. You do recognize, Sirius, that such behavior deserves punishment?"

Sirius stifles a yawn. "Of course, Mother."

"Regulus." Regulus looks around him with a start, suddenly far too aware that Mother's gaze is fixed upon him now. "My dear, were you at all aware of your brother's plans?"

Praying that she does not notice, Regulus chances to look at Sirius, who, very imperceptibly, shakes his head. "No, I wasn't. When I -- when I looked for him when I got off the train, he wasn't there."

"Ah." Mother nods. "And I see that, when you first came home, you failed to mention to me that your brother was missing?"

"I thought he would come home later," Regulus whispers, hoping that it is enough.

She returns her attentions to his brother, who appears quite preoccupied by the state of his robes. "Sirius, you are to be locked in your room for as long as you were away from home. Three days, you understand? Your things will be kept elsewhere, including that owl, and Kreacher will take care of you. Agreed?"

And both of her sons know that their agreement is irrelevant.

Shoulders hunched, Sirius leaves his things upon the steps. Mother watches him ascend to his bedroom and pitch himself upon his bed like a petulant little boy before she advances. She brandishes her wand and gives it a flick. The door to Sirius's room closes with a violent bang; the slight click of the lock is barely heard. She smiles at her handiwork.

"Regulus," she says slowly, "I hope that, when you are your brother's age, you are not nearly so difficult."

He thinks of the letter, partially composed, sitting upon his desk and manages some semblance of a smile. "I'll try, Mother."

-

Regulus is not the first person to see Sirius upon the cessation of his punishment. That honor belongs to Kreacher, who, not bothering to hide a scowl, has been given the responsibility of unlocking the door. Just as he snaps his fingers, the young master crashes out of the room. Sirius gives the house elf a shove before slipping his hands into his pockets and thundering down the stairs.

Regulus, still puzzling over the letter to Bellatrix, sets his quill down and listens. There's shuffling in the kitchen, the maddened clang of silverware.

"Hi," Regulus says, sliding into the kitchen.

Sirius looks up from the chunk of bread in his hand. "Can you believe this is all the food that's left in this house?"

"Kreacher must -- Kreacher must have forgotten to -- "

"Kreacher forgets too many damn things," Sirius snarls, gnawing off a mouthful of crust. "D'you know where Mum and Dad are?"

"With friends, I think."

"Friends." Sirius shakes his head, returning to his food.

From the corner of the room, Regulus watches him eat. There is a singular ferocity to the way he severs the bread and hunches over the table, his eyes boring into the plate before him. Has it always been there, Regulus wonders? Could it be the result of three days' punishment? Most likely not: both of them are quite used to Mother's punishments -- Sirius especially. Three days is nothing, really, compared to the time Sirius was kept in his room for a week, all for taking Cousin Narcissa's broom without first asking for permission --

"You can sit down, you know," Sirius says, interrupting Regulus's reminiscence.

He edges towards the table and pulls out the nearest chair. "You're not -- you're not angry with me, are you?"

"Reg, don't be thick." Sirius swallows whatever remains in his mouth before setting the remaining bit of bread back on the plate. He reaches across the table to tousle Regulus's hair. The latter squirms; Sirius had done that often when they were younger, but now, they are older. "Why would I be angry with my little brother, hmm?"

Regulus finds that his brother does not look so fearsome anymore, and there is a smile dancing around his lips. But there is no merriment in his gaze, which is too narrow, too detached to exude any sort of happiness. Regulus senses that none of this has anything to do with him.

-

The parchment is spotted, the handwriting hurried. Whereas Regulus had spent weeks struggling with his own letter, Cousin Bellatrix's reply is nonchalantly scribbled. _My flat, Tuesday evening._

He clutches the note in his fist as he approaches Mother, a book balanced upon her knees. Clearing his throat, she looks up, peering at him over her reading glasses. "Yes?"

"Mother, I -- Cousin Bellatrix invited me to her flat for -- " Regulus bites his lip, scrambling for an excuse " -- for tea next Tuesday. After dinner, I think. Would it be all right with you if I -- if I accepted her offer?"

"Of course, Regulus dear. Cousin Bellatrix is a good influence on you, I think, and her husband…well, a little disreputable, perhaps, but what a fine upstanding Pureblood. A Lestrange, Regulus! A Lestrange." She smiles, and for an instant, the characteristic beauty of the Black women glimmers from behind the curtain that age has draped over it. "It seems that there are so few of us left. You will heed any advice that your cousin gives you, no?"

Then Regulus is reminded as to why he is actually paying Bellatrix a visit, and any beauty there might have been in his mother disappears.

-

As the flames pull him through the bowels of London and to his cousin's flat, he recalls how much Sirius loves traveling by Floo powder. He has always thought it to be a great adventure, especially when he would none too accidentally lean one way or another and end up in the salon of a Parisian witch. Regulus momentarily considers doing the same, but he is already climbing out of the proper gate when the thought occurs to him.

Cousin Bellatrix and her newly obtained husband are waiting for him.

"Hello, Cousin Regulus," she says, stepping forward to kiss him once on each cheek. It is a gesture learned during her girlhood, one performed out of sheer habit, but no warmth lingers on his skin when she parts. "I'm not sure that you've been introduced to Rodolphus?"

Regulus regards him with a curt nod.

"Would you like some tea, cousin?" Bellatrix asks, giving her wand a wave. A porcelain cup dances out of the air. Steam is gently rising from the liquid within. Regulus takes the beverage and sips it slowly. The three of them stand there for a few moments, none of them speaking. Bellatrix gestures to the sofa behind her. "Please, sit."

As Regulus lowers himself onto the cushions, what she does not say is that he will be the only one sitting. The Lestranges will regard him from above. The message is clear: Regulus is naught more than a child where matters as important as these are concerned.

"I was most happy to receive your letter, to learn that you were interested in the offer I extended to you before your last term ended," she begins. Regulus has to tilt his head backwards to see her face. "Can I expect an answer from you now, or did you come here seeking more information?"

Regulus remembers the whispers over breakfast at the Slytherin table -- mutterings about blood purity and Muggles and one who styled himself as the Dark Lord, determined the save the wizarding world from itself. He thinks of his mother, beaming as she reported that her niece had married a Lestrange. He thinks of Sirius showing up at his home three days late, the Potters by his side as if -- as if, he thinks, his stomach convulsing, as if they were his family. "I think I know all that I need to know," he replies slowly.

He is too preoccupied with his tea to see Bellatrix and Rodolphus exchange glances.

"Excellent," she concludes. "So, Regulus, if I asked you to be here at this time next week, would you say yes?"

In one word, Regulus changes his life forever.

"Yes."

"Just don't wear anything too conspicuous," Rodolphus calls out as Regulus sprinkles Floo powder into the flames and watches them glow green.

-

He would not have done it if they were younger. That is Regulus's astonishingly poor defense for finding the door to Sirius's bedroom ajar and a half folded sheet of paper on his desk. He would not have done it if they were younger, but they are no longer so innocent.

He does not read much of it, only a sentence or two. He reads enough to understand that James Potter will be waiting, five streets south from here, prepared to flag down the Knight Bus at a moment's notice. Sirius needs only to send back his owl with a date and a time.

Underneath this letter is another scrap of parchment. As Regulus stumbles out of his brother's room, he cannot erase from his memory the words _next Wednesday, six in the morning? Sirius._

Sirius no longer needs his family, and Sirius no longer needs _him_.

-

"Cousin Bellatrix must brew some excellent tea," Mother says, smiling as Regulus steps into the fireplace.

Sitting in the corner, Sirius looks onward, indifferent.

-

The question is like a vein of gold running through the night, pressed to his eye until he can see nothing else -- nothing but the Muggle (middle-aged, female, and upstairs, her daughter is screaming) angled before him, ironed to the wall, nothing but his wand shuddering in his hand and Bellatrix standing before him, her head at a tilt. She is examining her handiwork.

"You weren't expecting this, were you?" she asks, almost tenderly.

Regulus shakes his head, bound by its mask. It cannot hurt to be honest. "Not really."

"What did you think we do -- sit on sofas and _talk_? Talk like our parents, cousin, who are too cowardly to do anything else?"

"What do -- " He swallows and hides the tremor in his voice " -- what does the Dark Lord gain from this?"

Even though he cannot see her face, he knows that she is laughing at him. "The Dark Lord? Regulus, this is just for fun."

Through the slits of his mask, he looks at the woman. Her eyelids flutter, her fingers twitch; a deep gash runs along the length of her arm, and scarlet rivulets drip from the exposed bone. "For fun," he repeats.

"It is also a test," she adds, her tone growing markedly more serious. "The Dark Lord cannot trust the loyalty of those who are halfheartedly committed to his goals. There is a certain -- a certain progression that must be followed before you can enter his inner circle, do you understand?"

"How high up are you?" Regulus prompts, aware that he is temporizing.

"Well, that isn't important to you. This is the most elementary of tasks, you see, recognizing Muggles for what they are: filth." Regulus mouths the word. _Filth_. "When, say, your room is dirty, you clean it, don't you? There's no need for all of that dust to be there. No need at all." Then she pauses. "You've never seen anyone cast an Unforgivable, have you?"

He grips his wand tighter now. "No."

"Ah, so I've a novice on my hands."

"Bellatrix!" a voice calls from the stairs.

"Be patient, Rodolphus," she hisses. Regulus turns around to see the older man skipping down the stairs, hands busily buttoning his trousers. "I am telling my cousin about how it all works."

"The girl upstairs is finished." A grin possesses his mouth. "I'll just watch, shall I?"

"You'll not talk anymore until _this_ one here is finished," Bellatrix mutters, jabbing her wand at the Muggle. The Muggle's head strikes the wall; Regulus cringes. "Right. Cousin, you do know of the Cruciatus Curse, yes?"

Suddenly, Regulus is five again, and his brother Sirius is standing in the backyard, waving his toy wand at a caterpillar, yelling _Crucio! Crucio! Crucio!_, all without ever realizing that toy wands are incapable of executing particular incantations and that the words issued from his mouth could earn him a stay at Azkaban. Regulus does not think that Sirius would do such a thing now. "Of course I know what the Cruciatus is."

Bellatrix nods towards her victim before pointing to a spot not three paces from the woman. "Cousin, I want you to stand here."

Regulus complies, and Bellatrix advances, her wand held out before her. The Muggle does not know what the Cruciatus is, but even on the verge of death, she has enough sense to recognize that there will be no respite from living pain, not yet. Her eyes are wide open now, white as ice as they watch Bellatrix inch nearer, and then she turns to him -- if he has never before seen someone beg for mercy, he is seeing it now as her lips form jagged, wordless pleas. Even now, she is broken, her child dead and raped, and she may dare to believe that he is enough of a man to tear off his mask, to throw himself between her and his cousin, and to declare this a forfeit -- or, at the very least, that he will be man enough to find some way of killing her first.

As the spell slips from Bellatrix's mouth and the woman's screams rent the sky, her wounds twitching, Regulus knows that he has never been the man of the family.

-

There is a bump outside his door, and Regulus stirs. The birds are singing to the sunrise, and there is blood, he realizes -- there is blood spotting his black robes, and that mask lying in the corner. Without pausing, he leaps to the bedroom door and throws it open.

Sirius is already halfway out the front door.

"Wait!" Regulus whispers as he chases his brother into the morning.

"Go back to bed."  
"You're running away, aren't you?"

Sirius sighs. "You sneak. Did you read my letter to James, or was that just a lucky guess?"

"Both, I think."

"Off to tell dear mother about me, then?"

"Sirius, I didn't tell her anything that first time -- just like you told me to. I love you, Sirius," he adds with a nod, but they both know equally well that the world cannot be explained by love alone. "I won't tell her about it, I promise."

"How do I know that I can _trust_ you, Regulus?" Sirius glares at him. "Oh, yes, I trusted you earlier. You saw me leave the station with James, and I knew that you wouldn't tell Mum anything. But -- look at you now. I never knew that you and dear Cousin Bellatrix were on such good terms. And you -- you think I can't see that you've got blood on your clothes?"

"Look, it isn't what you think it is."

"It is exactly what I think it is, Reg."

And that is when Regulus knows that the battle has begun. Sirius is leaving the Noble and Most Ancient House of Black for the refuge of the Potters, the blood traitors, and Regulus -- well, Regulus is unforgivable now.

Regulus shrugs. "I'm sorry, Sirius."

"No apology is going to help you get out of -- get out of whatever it is you've got yourself into."

"I'm still sorry."

It is Sirius's turn to shrug. "Tell Mum whatever you sodding want. It doesn't matter."

"Then why did you come home at all?"

Sirius pauses. His mouth twitches, as if he is trying to pass the whole matter off with a grin. "Because I love you, Reg."

The words are bitter.

Sirius picks up his trunk and casts a final look at the house of his childhood before turning away, walking towards the sunlight. Regulus watches him disappear.

-

A handful of hours later and donning a clean set of robes, Regulus finds his parents already at lunch.

"You slept through breakfast," Mother says.

Regulus rubs his eyes. They have seen too much in too little time. "I didn't sleep well last night."

"Is Sirius still asleep?"

Regulus blinks once. Twice. "Sirius is gone."

"For good?" Father asks, and Regulus swears that there is a note of hope in his question.

"I think so."

"Oh?" Standing up, Mother lays her fork and napkin down. "Regulus, follow me."

She leads him to the family tapestry. He is familiar with the relic, having spent hours kneeling before it as a child, memorizing the storied names of his ancestors. It is an old tapestry; he is afraid to touch it. Mother, however, seems to share none of his fears. Her finger traces the line down, down, down, until its tip reaches the very last fork. On one side, the name "Regulus Black," and on the other, "Sirius Black." Two scions, two brothers.

"This is what happens to blood traitors," Mother states, pulling out her wand and muttering something. There is a small explosion in the house, it seems, and when he looks again, there is only one Black brother remaining.


End file.
